1. Field of the Invention
The present invention relates generally to a downhole device that may be used to divert fluid flow out of a work string and into an annulus between the work string and tubing, casing, or the wellbore. The downhole device may be located at any point along a work string at which it may be necessary to divert the fluid flow to the annulus. The downhole device may be activated and/or deactivated by the movement of a plurality of pistons that are actuated by an increase in fluid pressure within the downhole device. Fluid flow through a restriction within the downhole device creates an increase in fluid pressure within the downhole device.
The increased fluid pressure moves the plurality of pistons downward within the downhole device. The pistons may be used to move a flow tube between various positions within the downhole device. In one position, the flow tube prevents fluid flow to the annulus while in another position the flow tube may allow fluid flow to be diverted to the annulus. The flow tube may be a longitudinal solid tube having a central bore along its entire length. A locating sleeve having a continuous j-track allows the flow tube to be selectively retained at the various locations within the downhole device. Fluid flow through the downhole device in combination with the locating sleeve may be used to cycle the device between diverting fluid flow to the annulus and preventing fluid flow to the annulus.
2. Description of the Related Art
In the oil and gas industry long tubular work strings are often used in drilling, completion, displacement, and/or work over operations. Often the work string is used to carry fluid down the well to a tool located at the end of the work string. For example, fluid may be circulated down a work string and out of a drill bit located at the end of the work string. Often drilling mud is pumped down the work string and through the drill bit. The drilling mud acts as a lubricant, but also carries the drill cuttings up the annulus around the work string to the surface.
Under certain circumstances it may be desirable to circulate fluid into the annulus surrounding the work string at a particular location. For example, the drilling mud may be entering into a porous well formation instead of properly circulating the drill cuttings to the surface. In this instance, it may be necessary to inject a sealing agent into the formation in an attempt to prevent the future loss of mud into the formation. A number of systems have been disclosed that enable the circulation of fluid to the annulus by dropping a device, such as a ball, down the work string.
U.S. Pat. No. 4,889,199 discloses a downhole device that allows annular circulation after dropping a plastic ball into the work string. The work string is broken at the surface and a plastic ball is dropped into the work string. The work string is then reconnected and fluid is pumped into the work string until the ball reaches the downhole device. The downhole device includes a shoulder that is adapted to catch the ball within the work string. Once seated on the shoulder the ball blocks the fluid flow through the work string and continual pumping of fluid causes fluid pressure to build above the seated ball. The device includes a ported sleeve that is adapted to move within the device. The sleeve is biased to an initial position by a spring. Once the force on the ball due to the fluid pressure is greater than the spring force, the ported sleeve moves within the device such that ports in the sleeve align with exterior ports in device allowing fluid to be circulated out of the work string into the annulus. When the sleeve is in its initial position the exterior ports in the work string are sealed preventing fluid flow to the annulus.
To remove the ball from the shoulder in the device, a number of smaller steel balls must be dropped into the work string, which again requires that the work string be disconnected at the surface. The number of steel balls inserted into the work string must be equal to the number of annular ports in the sleeve. The work string is then reconnected and fluid is pumped until the steel balls reach the downhole device. The steel balls are sized such that they fit within the sleeve ports blocking the fluid flow to the annulus. With the fluid flow to the annulus blocked by the steel balls and the fluid flow through the work string prevented by the plastic ball, the fluid pumped into the work string causes the fluid pressure within the work string to increase above the device until the plastic ball is deformed and pushed past the shoulder. The deformed plastic ball falls into a housing located at the bottom of the device. This allows fluid to once again flow through the work string past the device and the steel balls, which are sized smaller than the plastic ball, pass the shoulder and also are captured in the housing below the device. The sleeve is returned to its initial position due to the biasing spring until the next plastic ball is inserted into the work string.
There are a number of other systems that provide for annular flow out of the work string by dropping a device down the work string. Each of these systems requires that the work string be broken to drop a device each time that the fluid flow is to be diverted out of the work string. This process causes increases in well services costs as well as providing multiple opportunities for operator error. Further, the systems may require the use of multiple balls each cycle time the fluid flow is cycled. These balls may need to be removed from the work string or may alternatively be dropped into the well.
The use of a system that requires a device to be inserted down the work string to cycle the downhole device, such as a plastic ball, may make it difficult for operators or well service providers to accurately predict the amount of fluid pressure required to pass the ball past the shoulder within the device. The temperature within the well may cause the plastic ball to be a different size than at surface temperatures. The temperature within the well may also cause the dimensions of the shoulder to change, but because the shoulder is not comprised of plastic the change in shape may not correlate with the changes reflected in the ball. This may further make it difficult to predict the fluid pressure necessary to pass the plastic ball past the shoulder. It would thus be beneficial to provide a downhole device that may be cycled between preventing and providing annulus flow without the need of dropping a device, such as a plastic ball, down the work string.
There are other devices commercially available to divert fluid flow out of a work string to an annulus without the need to drop a device down the work string. These devices are often actuated by a pressure drop within the device that is created by increased fluid flow through a portion of the device having a restriction having a decreased flow area. This pressure drop must be sufficient to move a single component within the device, such as a piston or a sliding sleeve. However, in order to create an adequate amount of pressure to actuate the device the maximum flow area through the restriction is severely limited. Generally the current commercially offered diverting devices have a maximum diameter of ¾ inches through the restriction. Thus, it would be beneficial to provide a downhole device that did not require such a large decrease in flow area in order to actuate the device as this would allow a larger minimum flow area.
To divert fluid out of a work string, current systems generally require the alignment of ports of an inner sleeve or similar structure with the external ports in the housing of the device. The alignment of the inner ports with outer ports to allow the device to divert fluid to the annulus increases the complexity of the device. These types of devices may be susceptible to seal failure or inadequate flow if the ports are misaligned. It would be beneficial to provide a device that may divert fluid flow out of a work string without the need to align inner flow ports with external flow ports in order to divert fluid flow to the annulus.
In light of the foregoing, it would be desirable to provide a downhole device that has multiple pistons upon which an increase pressure may act to activate the device. It would be desirable to provide a downhole device that may be cycled between diverting and non-diverting modes, the downhole device having a larger flow bore. It would also be desirable to provide a downhole device that does not need to align the ports of an inner body with ports in an outer housing to divert flow out of a work string. It would be desirable to provide a downhole device that is actuated by an increase in fluid pressure due to fluid flow through a restriction, wherein multiple pistons were used to increase the inner diameter of the restriction. It would further be desirable to provide a downhole device for diverting fluid flow out of a work string that includes a secondary sliding sleeve that may be used to protect sealing elements. It would be beneficial to provide a downhole device that may be used to divert flow out of a work string having a minimum flow diameter of 1¾ inches.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the issues set forth above.